1. Field of The Invention
The invention relates to a low capacity nuclear reactor housed underground in the cavity of a cylindrical pressure vessel. More particularly, the invention relates to a reactor with a core or pile of spherical fuel elements, a blower forced downward, cooling gas flow, a removable metal core vessel, and a cover closing off the opening of the pressure vessel, wherein the cover is removable for installation and dismantling of the core vessel. The installation also includes a graphite reflector surrounding the pile on all sides and comprising a bottom, side and roof reflector arranged in part within the core vessel, and with a plurality of absorber rods displaceably located in the side reflector.
2. Description of the Related Technology
DE-OS No. 30 16 402 shows a high temperature modular reactor with a metal vessel containing the core of fuel elements located in the cavity of a concrete vessel closed off by a cover. The metal vessel, together with a metal base plate and the bottom, side and roof reflectors may be lifted from the concrete vessel following the shutdown of the reactor, discharge of the spherical fuel elements, dismantling of the control rods and opening of the cover. At least one pipe leading downward is connected to the base plate to remove heated cooling gas, which flows through the pile from bottom to top. The hot gas line leads to a second cavity, located parallel to the first cavity in the concrete vessel and in which a heat consumer, such as a steam generator, is installed. As an alternative to a second cavity, DE-OS No. 30 16 402 further proposes to extend the cavity containing the nuclear reactor downward and to place the heat consumer under the metal vessel.
German Application P No. 35 18 968.1, corresponding to co-pending U.S. Application Serial No. 866,921, discloses a further nuclear reactor. This nuclear reactor has a compact design and a far-reaching elimination of active operation installations, such as a charging apparatus, gas purification means, control systems, and safety systems. It is particularly suitable for the generation of thermal energy for heating purposes. The core vessel containing the pile of spherical fuel elements houses only part of the graphite bottom and side reflectors. Channels are provided in the part of the side reflector located within the core vessel for absorber rods, which serve trimming and shutdown purposes only. The roof reflector rests directly on the stationary pile of fuel elements. The entire core vessel and the components located therein are removed following burnup of the fuel elements. The heat generated in the core is transferred to a cooling system mounted on the inside of a pressure vessel enclosing the nuclear reactor by cooling gas flowing through the pile from top to bottom.
The state of the art further includes the nuclear reactor plant described in DE-OS No. 33 35 451, which relates to a high temperature reactor with spherical fuel elements. In this plant, all of the components of the primary loop, together with the control and shutdown devices are located inside a steel reactor pressure vessel in a manner such that they may be installed and dismantled from above. This enables use of an economical underground location. At least one removal tube is provided under the high temperature reactor for discharge of the fuel elements, said tube leading laterally out of the reactor pressure vessel.
DE No. 1 034 784 shows a gas cooled nuclear reactor with a pile of fuel elements of uniformly shaped bodies and similarly shaped pourable bodies for the reflector jacket.